/Engine/Source/Runtime/ApplicationCore/Public/GenericPlatform/Accessibility/GenericAccessibleInterfaces.h
Unregisters an accessible user from the accessible registry. If the passed in user index is not associated with a registered accessible user, nothing will happen. This function callsFGenericAccessibleUser::OnUnregisteredif the passed in user is successfully unregistered. Once an accessible user has been unregistered, the rest of the application should have no way of retrieving or interacting with the accessible user.
True if the accessible user with the associated user index is successfully unregistered. Else, returns false.
bool UnregisterUser ( const FAccessibleUserIndex UserIndex )